But the ACT government insists it was aware of the health risks linked to the banning of plastic bags, and ensured Canberrans were not put at any greater risk.

The research paper, dated November 2012, and published online in January by the University of Pennsylvania Law School’s Institute for Law and Economics, studied a connection between plastic bag bans in Californian counties and increases in food-related illnesses and death.

One study conducted in California and Arizona found most shoppers did not use separate bags for meat and vegetables, did not wash reusable grocery bags, and often stored them in car boots, resulting in the growth of bacteria.

“If individuals fail to clean their reusable bags, these bacteria may lead to contamination of the food transported in the bags. Such contamination has the potential to lead to health problems and even death,” the paper states.

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Focussing on a plastic bag ban introduced in San Francisco in 2007, the paper then compares the instances of emergency hospital admissions and deaths for food-related illness across counties with and without plastic bag bans, as well as across time periods before and after bans are introduced.

“We find that both deaths and ER visits spiked as soon as the ban went into effect,” the paper concludes.

“Relative to other counties, deaths in San Francisco increase by almost 50 per cent, and ER visits increase by a comparable amount. Subsequent bans by other cities in California appear to be associated with similar effects.”

The paper suggests washing reusable grocery bags could be the solution to health concerns, but could then have adverse environmental effects through increased use of water, detergent, and energy – in essence, nullifying the environmental benefits offered by banning plastic bags.

A spokesman for the ACT Environment and Sustainable Development Minister Simon Corbell said the government was aware of possible contamination, and chose made small plastic barrier bags - the bags customers tear from rolls in supermarkets - exempt from the territory's ban to reduce the risk.

‘‘The ACT government paid close attention to health and safety issues when implementing a ban on plastic bags in the territory,’’ the spokesman said.

‘‘This is why the ban in the ACT does not include plastic barrier bags (also known as bag-on-a-roll) used for fruit, vegetable, meat and seafood products,’’ he said.

The ACT’s plastic bag ban came into effect in November 2011. A recent survey conducted by the ACT government as part of an interim review of the policy showed 70 per cent of Canberrans want the ban to continue, while Greens minister Shane Rattenbury said the ban should be tightened to ensure all bags used in the capital are compostable.

The Canberra Liberals promised to overturn the bag ban if elected.

The research was undertaken by Pennsylvania Law School professor Jonathan Klick and George Mason University School of Law professor Joshua Wright, both of whom hold doctorates in economics.